Automatic switch for use in telephone or like systems



May 16, 1939. 7 SAXBY 2,158,384

' AUTOMATIC SWITCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed April 25, 1936 2 Sheets-Sheet l 4% I ///ii ///////i//// 8 N/ M/suurr/a/v l3 wan! //V $ULATION Arrr.

y 1939- R. N. SAXBY 2,158,384

AUTOMATIC SWITCH FOR USE IN TELEPHONE OR LIKE SYSTEMS Filed April 25, 1936 2 Sheets-Sheet 2 @9 ln/sUL/lT/ON 4 4 I I file".

Patented May 16, 1939 UNHTEB STATES @FFEQE AUTOMATIC SWITCH FOE USE EN TELE- PHONE OR LIKE SYSTEMS aware Application April 25, 1936, Serial No. 26,375 In Great Britain May 15, 1935 10 Claims.

The present invention relates to automatic switches for use in telephone or like systems and is more particularly concerned with improved contact-making wipers for use with such switches.

Generally in switches of this type the moving contact member comprises a pair of springy blades lying parallel to each other and given sufficient tension by bending that they make reliable electrical connection with a row of contacts. In

some cases the two blades may engage the same fixed contact on opposite sides and in other cases they engage two different fixed contacts which are separated by a thin layer of insulation.

It sometimes happens in the case of a twodirectional switch when the bank comprises a plurality of levels or rows of contacts, that manufacturing irregularities render it impossible for the wipers to be adjusted so that they cut into each level exactly in alignment with the contacts.

If this variation in the bank assembly exceeds the Working tolerances allowed, one or other of the wiper blades does not exert its proper effective pressure on the contact. This condition ives rise to doubtful electrical connection and is a possible cause of microphonic noises in speaking circuits. The chief object of the invention is to provide an improved wiper construction in which the wipers are automatically self-aligning and hence pressure compensation is duly taken care of.

According to one feature of the invention the tips of the wipers which engage opposite sides of the contact track are so mounted and mechanically interconnected that a force acting on one tip tending to separate it from its companion tip will produce movement of both tips without appreciable separation.

According to another feature of the invention the tips of the wipers which engage opposite sides of the contact track are prevented from moving more than a predetermined distance apart but are permitted to move as a unit in a direction transverse to the contact track.

The invention will be better understood from the following description of various methods of carrying it into effect, reference being had to the accompanying drawings comprising Figs. 1-12. Of these, Figs. 1 to 3 show diagrammatically various methods of obtaining compensation of pressure between the wiper bades to counteract bank irregularities and poor cut-in adjustment; Figs. 4 to 6 show perspective views of various arrangements of double'wiper blades suitable for use with the construction of Figs. 1 to 3; Figs. 7 and 8 show elevation and plan views of an actual wiper assembly embodying the features of Figs. 1 and 4; Figs. 9 and 10 show similar views of a slightly modified construction and Figs. 11 and 12 show a spring clip for supporting the wiper cords.

According to the construction shown diagram- 5 matically in Fig. 1, the shaft 7 carries a boss 8 to which a pair of thin flexible blades Ill and l I are secured. These blades are linked together at their free ends by means of an insulating washer i2 which seats in the depressions shown. It necl0 essary the wiper tips may be made somewhat stiffer than the supporting blades but in any event the effect of the washer is to localize the pressure at the tips so that it is maintained substantially constant on both blades over an appreciable are of movement of the blades about an axis transverse to the shaft i. The extent of this movement is limited by the fixed insulating memher 9 between the blades. In operation therefore a comparatively large amount of up-and-down 20 variation in the bank level is absorbed by the flexible blades without any appreciable eifect on the pressure between the tips which operate together as a single unit.

In the construction shown in Fig. 2, thin fiex- 5 ible blades are again employed but the tips are linked together by means of hook-shaped lugs I3 and 5% formed. out of the blades and acting on each other through a piece of insulating material !5. 30

According to the construction shown in Fig. 3, the wiper blades are made comparatively stiff and are freely pivoted at point 56 to the supporting bracket ii. The blades can thus swing transversely in a small arc, the limit of which is 35 governed by the fixed insulating tongue 18 extending from the supporting bracket but with suitably shaped tips no special tips need be taken to hold the blades in an intermediate position.

The reliability of contact under all conditions 40 may be still further increased by providing special arrangements for overcoming trouble due to dust or the like. One method is to employ wiper blades having twin tips which conveniently make contact on the same radial line and are located one 45 upon the other so as to permit slight relative movement in a direction transverse to the contact track. Fig. 4 shows a twin tip wiper blade adapted for movement over the contact bank in either direction and conveniently formed from a press- 50 ing having the tips projecting in opposite directions by bending back the tip originally pointing towards the shaft. This type of blade is suitable for use with the construction of Fig. 1, which has. the tips linked together by means of an insulating 55.

washer. In the arrangement of Fig. 4 provision is made by means of the notch shown for linking together only the inner pair of tips as this is found to be effective on the outer pair owing to the stiffness of the tip construction as compared with the flexibility of the connection to the shaft. By changing the wiper tips from substantially V shape to a spoon shape (not shown), the life of the tip may be prolonged. Under conditions of constant use the spoon shape offers a progressively increasing area of contact which tends to reduce the rate of wear. The width of the tips is preferably made less than the distance between two adjacent bank contacts to obviate any possibility of worn wipers bridging two contacts.

Fig. 5 shows a twin tip blade of the trailing type suitable for use with the construction of Fig. 2 and adapted to move over the contact bank in one direction only. Again only the inner pair of tips are linked since the linking is efiective on both pairs of tips for the reason already explained.

Fig. 6 shows a twin tip of the trailing type suitable for use with the construction of Fig. 3 and in this instance any special linking together of the tips is unnecessary since they are comparatively rigid.

Referring now to the actual wiper assembly shown in Figs. '7 and 8, it will. be seen that this is mounted on a pair of lugs l9 and 28 extending from a bracket member 211 clamped to the tubular wiper carriage or shaft 22 of the switch. The blades themselves are mounted on opposite sides of a plate of insulating material 23 and supported on the lugs by means of the screws and insulating washers 24. The insulated plate 23 is extended forwardly between the wipers so as to prevent contact between them and also serves to set a limit to any vibration which may develop during vertical stepping owing to the extreme flexibility of the blades. Each of the blades is formed as a single pressing of brass or other suitable material provided on one side with a terminal tag 25 and having tips initially projecting in opposite directions, the twin contact effect being obtained by bending the inside tip back over the other as shown.

The arrangement shown in Figs. 9 and 10 is substantially similar to that shown in Figs. 7 and 8. It will be seen that the wiper assembly is mounted on the lugs 30 and 3| projecting from a bracket member 32 which is clamped to the shaft 33 by means of strap 34 and screw 35. The wipers 36 and 3'! are in this case of a slightly different shape and are held together by the insulating collar 38. Moreover twin tips are not provided but the tips 39 are spoon shaped which has the advantages mentioned above in connection with wearing properties. The separating insulator 40 in this case projects rather further from the shaft and extends to a short distance from the wiper tips. The terminal tags 4| and 42 are not integral with the wiper itself but are held by thescrews 43 and 44 so as to be pressed into contact with the appropriate wiper when the screws are tightened up.

The flat hairpin spring shown in Figs. 11 and 12 is adapted to be pushed on to the wiper carriage 22 so that it clips into position and is provided with a pocket 26 for supporting the wiper cords. The edges of the pocket are turned over as shown to prevent abrasion of the cords while one of the free ends is made somewhat longer than the other and provided with a notch 21 which registers with the edge of the insulating plate 23 separating the wipers so as to locate the spring in its mounted position.

The invention therefore provides a very simple construction whereby the reliability of contact in switches of the type considered may be considerably increased, this desideratum. being particularly important in the case of wipers carrying speech currents where imperfect or variable contact gives rise to parasitic noises.

I claim:

1. In a mechanical switch, a pair of wipers each having a tip for engaging opposite sides of a bank contact, an insulating member interconnecting said wipers and detachably retained by the configuration and relative position thereof so that a force acting on one wiper tip to separate it from its companion wiper tip moves both tips in the same direction without appreciable separation therebetween, and means for limiting to a predetermined amount the movement of both of said tips in said direction.

2. In a mechanical switch, a wiper assembly comprising wipers with an insulating yoke, tips on said wipers for engaging opposite sides of a bank contact, said wipers formed and in relative position to retain said yoke for preventing the separation of said wiper tips more than a predetermined distance While permitting said wiper tips to move as a unit in a direction transverse to said bank contact, and means for limiting to a predetermined amount the movement of said tips as a unit.

3. In a mechanical switch, a wiper assembly comprising flexibly mounted wipers, tips on said wipers for engaging opposite sides of a switch bank contact, and a collar encircling said wipers for preventing the separation of said wiper tips more than a predetermined distance while permitting said wiper tips to move as a unit in a direction transverse to said bank contact.

4. In a mechanical switch, a wiper assembly comprising flexibly mounted wipers, tips on said wipers for engaging opposite sides of a switch bank contact, hook members on adjacent sides of opposite wipers interlocked for preventing separation of said wiper tips more than a predetermined distance while permitting said wiper tips to move as a unit in a direction transverse to said bank contact, and means for limiting to a predetermined amount the movement of said tips as a unit.

5. In a mechanical switch as claimed in claim 2 including a fixed insulating member located between said wipers for limiting the transverse movement thereof.

6. In a mechanical switch, a wiper assembly comprising wipers mounted one upon the other with a collar encircling the two innermost wipers, tips on said wipers for engaging the switch bank contacts, two of said tips engaging the same side of a bank contact, while two other tips engage the other side of said contact, and said innermost wipers formed so that said collar may be detachably retained for preventing the separation of said wiper tips more than a predetermined distance while permitting said wiper tips to move as a unit in a direction transverse to the switch operating movement.

'7. In a mechanical switch, a wiper shaft, a wiper assembly mounted on said shaft and comprising a plurality of wipers, said wipers having special configurations, contact points on said wipers for engaging opposite sides of a switch bank contact, and means detachably retained by the relative position of said wipers and said configurations thereon for moving said wipers as a unit when a force is exerted on only one of said wipers.

8. In a mechanical switch, a wiper shaft, a wiper assembly mounted on said shaft and comprising a plurality of wipers, contact points on said wipers for engaging opposite sides of a switch bank contact, insulating means retained by the relative position of said wipers for moving said wipers as a unit when a force is exerted on only one of said wipers, and means for limiting said movement to a predetermined amount.

9. In a mechanical switch, a wiper shaft, a wiper assembly mounted on said shaft and comprising a plurality of wipers, contact points on said wipers for engaging opposite sides of a switch bank contact, means including a single member detachably retained by the relative position of said wipers for moving said wipers as a unit when a force is exerted on only one of said wipers, and means comprising a stop member mounted on said shaft and adapted to be engaged by said wipers during movement thereof for limiting the movement of said wipers as a unit to a predetermined amount.

10. In a mechanical switch, a wiper shaft adapted for rotation, a wiper assembly mounted on said shaft for rotation therewith and com prising a plurality of Wipers, contact points on said wipers for engaging opposite sides of a switch bank contact, and means detachably retained by configuration and tension of said wipers for moving said wipers as a unit in a direction transverse to the direction of rotation of said Wipers when a force is exerted on only one of 15 said wipers.

ROBERT NORMAN SAXBY. 

